Adjustable dovetail boring bar

ABSTRACT

The specification discloses a boring bar having shanks with a head mounted on one end and with a dovetail tongue and groove connecting the head to the shank. A clamp screw extending through the groove and also through the tongue is provided for clamping the shank and the head together.

United States Patent [1 1 Even-sole ADJUSTABLE DOVETAIL BORING BAR [75]Inventor: William C. Eversole, Latrobe, Pa.

[73] Assignee: Kennametal lnc., Latrobe, Pa.

[22] Filed: May 25, 1972 [21] Appl. No.: 257,051

Related US. Application Data [63] Continuation-impart of Ser. No.89,186, Nov. 13,

1970, abandoned.

[52] US. Cl. 408/181, 408/185 [51] Int. Cl B23b 29/34, B23q 3/12 [58]Field of Search 408/153, 156, 181, 185

[56] References Cited UNITED STATES PATENTS 3,704,958 12/1972 Gulibon etal. 408/181 [111 3,801,213 i451 Apr. 2, 1974 2,034,453 3/1936 Wiener408/181 X 1,287,971 12/1918 Groff 408/181 X 3,433,104 3/1969 Milewski etal 408/156 Primary Examiner-Francis S. Husar Attorney, Agent, orFirm-Melvin A. Crosby {5 7] ABSTRACT The specification discloses aboring bar having shanks with a head mounted on one end and with adovetail tongue and groove connecting the head to the shank. A clampscrew extending through the groove and also through the tongue isprovided for clamping the shank and the head together.

9 Claims, 4 Drawing Figures PATENTEMPR 2 i974 FIG-4 24 INVENTOR. WILUAMC. -EVER5OLE "M a-W ADJUSTABLE DOVETAIL BORING BAR This application is acontinuation of my prior application, Ser. No. 89,186, filed Nov. 13,1970, and abandoned simultaneously with the filing of the presentapplication.

The present invention relates to boring bars and is particularlyconcerned with a boring bar having an adjustable head, especially a headwhich is radially adjustable.

Boring bars having adjustable heads are known but, heretofore, have beensomewhat expensive to manufacture and have been lacking in the supportof the head on the shank of the bar. For the reason that the head wasnot extremely rigidly supported on the shank,

such boring bars have generally been used only for taking relativelylight cuts.

Still further, such bars have sometimes been provided with safetyinter-locks between the heads and shanks thereof to prevent the headfrom accidentally becoming disengaged from the shank in case the machineoperator should forget to tighten up the clamp screw, or in case of theclamp screw breaking, or by reason of some other fault occuring inrespect of the clamping of the head to the shank.

With the foregoing in mind, the primary object of the present inventionis the provision of a boring bar with a shank and a head thereon whichis adjustable laterally relative to the axis of the shank in which thehead is extremely solidly supported on the shank while the head ispositively prevented from becoming disengaged from the shank by the samescrew which effects the clamping up operation.

Another object of the present invention is the provision of anadjustable head boring bar structure which is relatively inexpensive tomanufacture.

Still another object of the present invention is the provision of aboring bar of the nature referred to which permits relatively heavy cutsto be taken by a cutting insert carried by the head without any dangerthat the head will shift or deflect on the boring bar.

These and other objects and advantages of the present invention willbecome more apparent upon reference to the following detailedspecification taken in connection with the accompanying drawings inwhich:

FIG. 1 is a perspective view showing a boring bar with adjustable headaccording to the present invention;

FIG. 2 is a side view of the boring bar and cutting head partly brokenaway;

FIG. 3 is a plan sectional view indicated by line III- III on FIG. 2;and

FIG. 4 is a transverse vertical sectional view indicated by line IV-IVon FIG. 2.

BRIEF SUMMARY OF THE INVENTION The present invention relates to a boringbar having a radially adjustable head thereon. The adjustable head isconnected to the boring bar by way of a dovetail having a relativelywide angle and a screw is provided for clamping the boring bar part ofthe dovetail connection to the part of the connection carried by theboring head and is arranged to extend directly through the dovetailportion carried by the adjustable head thereby providing for greatstrength and rigidity of connection of the head to the boring bar andeliminating the possibility of DETAILED DESCRIPTION Referring to thedrawings somewhat more in detail, the boring bar illustrated thereincomprises a shank portion 10 which is an elongated generally cylindricalmember adapted for being clamped in a suitable support therefor in amachine tool. The work may rotate relative to the boring bar or theboring bar may be r0- tated relative to the work. The boring barillustrated is adapted for either type of operation. Shank 10 preferablyhas flats 12 formed thereon and extending longitudinally of the shankand providing convenient surfaces for nonrotatably clamping the shankfixedly to the support therefor.

At the one end, shank 10 carries a head 14 which has a pocket 16 inwhich a cutting insert 18 is clamped as by a top clamp member 20.

The head 14 on the side thereof facing the shank 10 is flat and isprovided with a rearwardly protruding lateral extension on tongue 22adapted for being slidably received in a lateral slot or groove 24 inthe adjacent end of shank 10. Tongue 22 advantageously has an axiallyextending planar bottom surface 26, a diametral rear surface 28 and atop surface which comprises an axial portion 30 remove from the head andan inclined portion 32 adjacent the head. The tongue 22 is thus in theform of a one-sided dovetail having an inclinedsurface on only one sidethereof.

Shank 10 has a flat end thereon into which a diametral groove 24 isformed. The groove 24 in shank l0, similarly to tongue 22, has a bottomaxially extending planar surface 34, a diametral rear surface 36, and aI top surface comprising the axially extending portion 38 remote fromthe end of the shank and the inclined front part 40 adjacent the end ofthe shank and which is complementary to portion 32 of the top wall oftongue 22 on the head 14.

The boring bar, furthermore, includes a slot 42 extending generallyaxially of the boring bar from the bottom of groove 24 preferably at ornearthe juncture of the back wall 36 and portion 38 of the top wall ofthe groove 24 in the shank 10 of the boring bar. Slot 42 could belocated anywhere along the back wall of groove 24 but is advantageouslylocated as shown near the juncture of the aforementioned back wall andtop wall portion of the groove for the reason that this location of theslot imparts the best action to the clamping up operation and likewiseresults in the strongest construction.

According to the present invention, the interengaging dovetail surfaces32 and 40 are inclined at an angle of about 45 degrees to the axis ofshank 10, although it will be understood that this angle could varysubstantially within the purview of the present invention. The importantthing about the angle of the inclined surfaces is that whenthe assemblyis clamped together, the head be drawn toward the shank so the flat sideof the head will firmly engage the flat end of the shank so the headwill be exactly located and will be held against yielding, even underfairly high loads.

' The flat end of shank l0 referred to is a planar end surface 44 andthe flat side of the head 14 referred to facing shank 10 is a planarsurface 46 for engagement with surface 44.

According to the present invention, the tongue 22 on the head of theboring bar is provided with a laterally elongated hole 48 to receive aclamp bolt 50 with clearance. Hole 48 could be in the form of a recessextending into said tongue from the rear end but is preferably in theform of a hole to keep the tongue as strong as possible.

Clamp bolt 50, as will best be seen in FIGS. 2 and 4,

. has a head 52 receivable in a recess 54 provided therefor in the shankin the region of the end of shank 10 adjacent head 14. Recess 54 iscoaxial with a bore 56 in the shank which is threaded .for receiving thethreaded end of screw 50.

The location of screw 50 is of particular merit because it acts directlyin the vicinity of the transverse plane of the inclined surfaces 32 and40 and is thereby highly effective for drawing these surfaces tightlytogether, and, furthermore, for holding the surfaces in firm engagementonce the screw has been tightened up.

Still further, the screw 50 passes through hole 48 with clearance andthis is of particular merit because, if it should happen that themachine operator inadvertently forgetsto tighten up the clamping screw,the head 14 cannot be thrown off from the shank 10 even when the boringbar is of the rotating type.

As mentioned, the screw holds the assembly tightly clamped together andthis is of importance because it permits relatively heavy cuts to betaken by a boring bar according to the present invention without theload imposed on the insert carried by the head causing any tiltingof theMarion shank l0.

If the screw 50 were to be located rearwardly along a shank from head14, as is the case in respect of certain other knowntypes of adjustablehead boring bars, one thereof being shown in the U.S. Pat. No.3,433,104, there would be sufficient resilience in the assembly topermit the head to tilt under extremely heavy loads and this is, ofcourse, highly objectionable.

The location of slot 42 near the top of the back wall of the groove inthe end of shank 10 is important because the lower part of the boringbar remains a solid mass of metal and is, thus, in the best possiblecondition to sustain any thrusts imposed on the insert carried by thecutting head.

Assuming that the principal load on the cutting insert is downwardly asindicated by arrow 60 in FIG. 2, it will be evident that the tang on thetop of the boring bar formed by the notch 42 and including at its outerend the wedge shaped portion that fits in the dovetail formed on thetongue 22 of the head, the said tang will be principally in tensionwhile the surfaces 44 and 46 toward the bottom of head 14 will be placedprincipally in compression.

- The disclosed arrangement thus forms an extremely strong and solidmounting for the head 14 of the boring bar and, furthermore, eliminatesthe possibility of injury to the shank 10 in the case of sudden shockloading on the head as can sometimes occur during machining operationswhen an insert breaks or when certain other unexpected events occur.

The invention also proposes the provision of an adjustrnent screw 62extending laterally into tongue 22 in the plane in which screw 50 islocated. The region of the tongue 22 immediately surrounding the holefor screw 62 may have indicia 64 thereon so the amount of rotation ofthe screw and, therefore, the amount of adjustment laterally of head 14on shank 10 can be determined.

It would be possible, of course, to include a further adjusting screwextending into tongue 22 from the opposite side of screw 62, if sodesired, but in most cases, a single adjustingscrew is adequate foreffecting radial adjustment of head 14 on shank l0.

Inasmuch asthe clamp screw extending through the groove and tongue alsorepresents a safety feature inasmuch as it prevents the head frombecoming disengaged from the shank, it is possible further to enhancethe safety aspect of the arrangement by providing a slightly weakenedregion in the clamp screw adjacent the head end, as shown at 53, so thatif the clamp screw should, for any reason, become stressed to the pointof breaking, the fracture will occur at the weakened region of the screwthereby leaving in the shank that portion of the screw extending intothe tongue on the head so that the head will be held on the shank tillthe machine can be brought to a halt and suitable repairs made in theboring bar, or the boring bar replaced by another.

Modifications may be made within the scope of the appended claims.

What is claimed is:

l. A boring bar comprising an elongated shank having a longitudinalaxis, a separable head at one end of said shank adapted for supporting acutting insert, said shank and head having respective opposed flatsurfaces perpendicular to the longitudinal axis of said shank, a grooveformed in one of the side of said head facing said one end of said shankand the-said one end of said shank and a tongue on the other thereofclosely fitted into said groove, said tongue and groove extending in thediametral direction of said shank and substantially at right angles tothe longitudinal axis of said shank, a clamp screw in the one of saidshank and head having the groove formed therein and extending at rightangles to the longitudinal axis of said shank and to said diametraldirection and also extending through said tongue,

said tongue having an opening receiving said clamp screw and elongatedin said diametral direction, threaded. means operatively interposedbetween said head and shank and acting in saiddiametral direction andadjustable for effecting adjustment of said head and shank relatively insaid diametral direction, said tongue being of substantial size in crosssection, one side wall of said tongue and the one side wall of saidgroove which is adjacent thereto being planar and parallel to thelongitudinal axis of said shank, the other side wall of said tonguecomprising a first portion adjacent the respective flat surface which isinclined so as to diverge from the longitudinal axis of said shank in adirection away from said respective flat surface and a second portionremote from said respective flat surface which is parallel to thelongitudinal axis of said shank, the other side wall of said groovehaving a first portion parallel to said first portion of the other sidewall of said tongue for engagement therewith when said clamp screw istightened and a second portion substantially parallel to said secondportion of the other side wall of said tongue and spaced therefrom whensaid clamp screw is tightened, the bottom wall of said tongue whichfaces the bottom wall of said groove being spaced from the bottom wallof the groove when the said opposed flat surface on said head and saidshank are interengaged.

2. A boring bar according to claim 1 in which the one of said shank andhead having the groove formed therein includes a slot extending from thebottom wall of said groove generally in the longitudinal direction ofsaid shank.

3. A boring bar according to claim 1 in which said groove is formed insaid shank and said tongue is on said head.

4. A boring bar according to claim 1 in which said head on the sidethereof which faces away from said one end of said shank comprises apocket formed therein for receiving an insert, said pocket having abottom wall on which an insert placed therein rests and disposedsubstantially in a plane extending parallel to said longitudinal axis ofsaid shank and also parallel to said diametral direction.

5. A boring bar according to claim 3 which includes a transverse slotformed in said shank and extending generally axially thereof from thebottom wall of said groove in a direction away from said one end of saidshank.

6. A boring bar according to claim 5 in which said slot is located nearthe juncture of the said bottom wall of said groove with the said secondportion of said other side wall of the groove.

7. A boring bar according to claim 1 in which the side of said headwhich faces away from said shank is formed with a pocket to receive acutting insert, said pocket having a bottom wall on which an insertdisposed in the pocket is supported, said bottom wall of said pocketbeing disposed in a plane substantially parallel to the longitudinalaxis of said shank and to said diametral direction, said bottom wall ofsaidpoeket facing away from the said one side wall of said tongue,whereby an insert mounted in said pocket and presented a cutting edge toa work member will have the principal load thereon directed toward thesaid one side of said tongue and groove.

8. A boring bar according to claim 1 in which the angle between theplane of the said flat surface on said head and the plane of said firstportion of said other side wall of said tongue is about 45.

9. A boring bar according to claim 1 in which said clamp screw comprisesa weakened region near the head.

1. A boring bar comprising an elongated shank having a longitudinalaxis, a separable head at one end of said shank adapted for supporting acutting insert, said shank and head having respective opposed flatsurfaces perpendicular to the longitudinal axis of said shank, a grooveformed in one of the side of said head facing said one end of said shankand the said one end of said shank and a tongue on the other thereofclosely fitted into said groove, said tongue and groove extending in thediametral direction of said shank and substantially at right angles tothe longitudinal axis of said shank, a clamp screw in the one of saidshank and head having the groove formed therein and extending at rightangles to the longitudinal axis of said shank and to said diametraldirection and also extending through said tongue, said tongue having anopening receiving said clamp screw and elongated in said diametraldirection, threaded means operatively interposed between said head andshank and acting in said diametral direction and adjustable foreffecting adjustment of said head and shank relatively in said diametraldirection, said tongue being of substantial size in cross section, oneside wall of said tongue and the one side wall of said groove which isadjacent thereto being planar and parallel to the longitudinal axis ofsaid shank, the other side wall of said tongue comprising a firstportion adjacent the respective flat surface which is inclined so as todiverge from the longitudinal axis of said shank in a direction awayfrom said respective flat surface and a second portion remote from saidrespective flat surface which is parallel to the longitudinal axis ofsaid shank, the other side wall of said groove having a first portionparallel to said first portion of the other side wall of said tongue forengagement therewith when said clamp screw is tightened and a secondportion substantially parallel to said second portion of the other sidewall of said tongue and spaced therefrom when said clamp screw istightened, the bottom wall of said tongue which faces the bottom wall ofsaid groove being spaced from the bottom wall of the groove when thesaid opposed flat surface on said head and said shank are interengaged.2. A boring bar according to claim 1 in which the one of said shank andhead having the groove formed therein includes a slot extending from thebottom wall of said groove generally in the longitudinal direction ofsaid shank.
 3. A boring bar according to claim 1 in which said groove isformed in said shank and said tongue is on said head.
 4. A boring baraccording to claim 1 in which said head on the side thereof which facesaway from said one end of said shank comprises a pocket formed thereinfor receiving an insert, said pocket having a bottom wall on which aninsert placed therein rests and disposed substantially in a planeextending parallel to said longitudinal axis of said shank and alsoparallel to said diametral direction.
 5. A boring bar according to claim3 which includes a transverse slot formed in said shank and extendinggenerally axially thereof from the bottom wall of said groove in adirection away from said one end of said shank.
 6. A boring baraccording to claim 5 in which said slot is located near the juncture ofthe said bottom wall of said groove with the said second portion of saidother side wall of the groove.
 7. A boring bar according to claim 1 inwhich the side of said head which faces away from said shank is formedwith a pocket to receive a cutting insert, said pocket having a bottomwall on which an insert disposed in the pocket is supported, said bottomwall of said pocket being disposed in a plane substantially parallel tothe longitudinal axis of said shank and to said diametral direction,said bottom wall of said pocket facing away from the said one side wallof said tongue, whereby an insert mounted in said pocket and presented acutting edge to a work member will have the principal load thereondirected toward the said one side of said tongue and groove.
 8. A boringbar according to claim 1 in which the angle between the plane of thesaid flat surface on said head and the plane of said first portion ofsaid other side wall of said tongue is about 45*.
 9. A boring baraccording to claim 1 in which said clamp screw comprises a weakenedregion near the head.